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2WD-4WD mode change malfunction

Discussion in '3rd Gen. Tacomas (2016-2023)' started by YotaEmma, Jul 12, 2020.

  1. Jul 15, 2020 at 11:35 PM
    #61
    kgilly

    kgilly Well-Known Member

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    Kurt
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    Bed cover and Mud flaps, OEM Audio, Super Bump stops, Sumo Springs, Bed Stiffeners, Stryker hood shocks
    you can drive it in 4Hi on a limited basis on dry pavement in order to get to a good location, just take your time while doing it
     
  2. Jul 16, 2020 at 4:00 AM
    #62
    6 gearT444E

    6 gearT444E Certified Electron Pusher

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    The ECU is almost never the problem. The grease monkeys that work at Toyota use that as an excuse since it’s a high dollar value for them to replace and it’s a couple plugs and a screw. They are too lazy to diagnose the real problem and tack that big dollar item on the bill so they can have their Twix bar at lunch.
     
    Taco Tyrant and YotaEmma[OP] like this.
  3. Jul 16, 2020 at 4:21 PM
    #63
    YotaEmma

    YotaEmma [OP] Member

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    So guys got my truck back, guy said they replaced the ecu and the ADD actuator, but it’s bullshit because the invoice doesn’t say say they replaced the ECU.

    They only replaced the ACC actuator

    they did a health check and found a code (P17A9) in 4 wheel drive Ecu.


    And found an intermittent short to ground
     
  4. Jul 16, 2020 at 5:31 PM
    #64
    Sharpish

    Sharpish Well-Known Member

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    You’ll be fine, as was already said the ADD often goes bad and the ECU never goes bad. Try it out and let us know!
     
    YotaEmma[QUOTED][OP] likes this.
  5. Jul 16, 2020 at 5:39 PM
    #65
    ShimStack

    ShimStack Well-Known Member

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    As everyone said it's never the ECU and always the ADD actuator. The ECU's are tough and the 4wd ECU is tucked safely behind the dash. The ADD actuator is a bit flimsy and out in the elements.
     
    YotaEmma[OP] likes this.
  6. Jul 17, 2020 at 8:22 AM
    #66
    BigWhiteTRD

    BigWhiteTRD Official thread killer (only crickets remain)

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    As has been said, dont freak out over the ECU.
    All anecdotal evidence says that ECU is OK, and whomever told you different was probably just misinformed...

    Based on what you posted, it all seems to check to me. The ECU stores the issues, even if the issue clears up between runs and no MIL currently is shown... It appears they pulled the code and it showed motor current leakage to ground for the actuator (which implies that the ECU is alive and well). This is much like a GFCI, where the ECU detects that current is being lost in the circuit to ground (where it shouldn't be going).

    They then located an intermittent short to ground. This could be as simple as a chafed wire or debris in the ADD actuator, or a damaged wire. On at least one occasion I know water in the ADD actuator will cause that exact code and damaged the actuator.

    If they replaced the ADD, I would expect that to fix the current issue.
    However, if it were my truck I would change the front diff oil unless you have more data of what was wrong in the ADD actuator. If it was a debris that caused the short, I would change the front diff oil, if it was water I would change the front diff oil, if it was a shorted wire I would still probably change the diff oil...

    While you are in there, do a good visual check to see if the vent line is installed correctly on the front diff actuator and look for cracks, heat or physical damage, etc to the tube...

    The thing with this 4wd system is that is ALOT more self protection built-in compared to the old systems, and it defaults to locking out mode changes when it detects anything wrong
     

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